As is now known in the valve art, use of a one-piece ball and shaft element in ball valves not only simplifies construction of the valve and the valve body or housing but also solves many problems associated with sealing the area therebetween and maintaining a fixed relationship between the ball and shaft.
It is also known that valves having a one-piece ball and shaft construction are advantageous since backlash and deadband problems do not occur when trying to accurately position the ball for use as a flow control valve since there is no possibility of dead spaces being created in the joint as might occur with a separate ball and shaft construction.
The present invention also relates to ball valve assemblies which are particularly useful in extremely high and low temperature environments and one embodiment allows easy in-line servicing of the ball and valve seats.
As examples of prior known devices incorporating one-piece ball and stem arrangements reference can be made to U.S. Pat. No. 3,445,087 and Canadian Pat. No. 978,172.
As indicated above, it is extremely desirable to have ball valve assemblies which are useful in environments having both very high and very low temperature conditions. However, there are several known problems in these use areas. The major difficulties relate to thermal expansion and contraction which requires the proper fitting of parts under highly varying temperature conditions and the proper sealing of body openings and joints. When reference is made to very high and very low temperatures very high temperatures are considered to be those ranging between 1000.degree. to 2000.degree. F. while very low temperatures are considered to be those below -100.degree. F.
Another major problem which can affect the long term functioning of ball valves, especially in very high temperature applications, relates to the presence of abrasive solids in the fluid whose flow is being controlled. Gases resulting from combustion processes often include fly ash and in the minerals or mining industries mineral ore solids or coal or char particles can often times be entrained within the flowing gas or fluid resulting from such operations. Accordingly, it is highly desirable to have a valve construction that allows for the presence of abrasive solids within the flowing fluid so that the valve will not be affected by their presence.
The present invention provides a convenient solution to each of the above difficulties and in addition exhibits a structure that allows for much improved and easier serviceability including improved in-line servicing of the ball and stem element as well as the internal seals directly engaging the ball.
The present invention also provides a ball valve assembly that includes excellent sealing capabilities between the ball and the valve body or in particular between the ball and separate elements inserted within the valve body which form together with the ball the fluid flow path.
The present invention also makes use of solid form springs behind the bearings and solid elastically compressible behind the seat seals which assures that the cavity behind the bearings and the valve seats are filled with a solid material so that additional solids cannot enter and cause difficulties. Also, use of solid springs behind the bearings assures that those bearings are continuously thrust inwards onto the ball thereby preventing solids from entering between shaft and inside bore of the bearing while at the same time completely filling the space they occupy so that additional solids cannot enter.
The present invention is set forth herein in the form of two embodiments, the first not being serviceable in-line and a second having full in-line serviceability of the ball and stem element as well as the valve seats.
Both embodiments employ a one-piece valve body structure which includes preferably two perpendicularly positioned cross bores therethrough. It is preferable that these cross bores are centrally located in the valve body but it should be understood that it is essential that only one of these bores be a through bore so that the second bore could extend perpendicularly from that through bore to the outside of the valve body in only one direction. Of course in this latter case the ball would have only one stem or shaft disposed in that second bore. Each ball stem element is provided with a trunnion bearing and the ball and stem structure is suitably supported in the valve body by annular enclosing and sealing elements which both rotatably support and seal the ball stem. In each instance, the bore or opening in which the ball stem is incorporated is concentric with respect to the axis of rotation of that ball stem and is dimensioned so as to be at least as large or larger than the diameter of the ball element itself. Further, in the second embodiment the bore in which the ball stem is positioned is also large enough to allow removal of the valve seats.
Each embodiment includes separate, end members, preferably identical, which are inserted into opposite sides of the bore extending through the valve body and which form, together with the bore the ball element, the fluid conducting passage in the ball valve assembly. These end members can be turned or machined parts which also simplifies construction. In the first embodiment, the end members include inner end portions shaped in a cooperative and corresponding fashion with the shape of the outer surface of the ball to facilitate effective and complete sealing of the flow path through the valve. To complete that seal, the inner end of each end member is provided with an annular valve seat constructed from a solid material such as metal, or a synthetic resin such as polytetrafloroethylene.
In the second embodiment, the portion of each end member which extends into the valve body is foreshortened and provided with a convex, generally spherically shaped inner end. A separate cylindrical extension member is disposed between the spherical inner end of each end member and the ball element so as to also form a link in and part of the valve's flow path. The valve body itself is shaped to provide a recess above the area where the cylindrical members are located to provide an empty area into which the cylindrical members can move. Each cylindrical member has an inner ball engaging and an outer end member engaging member. The outer end is shaped to correspond to the shape of the inner end of the end members and an inner end adjacent the ball element which is shaped to correspond to the shape of the surface of the ball element. The inner edge is also provided with two beveled edges both of which face axially outwardly with the innermost edge facing radially inwardly and the outermost edge facing radially outwardly. An annular valve seat and seal is also provided in the inner end and is similar in function and design to the valve seat and behind the seat seal used in the first embodiment.
When the annular enclosing and sealing member in the second embodiment is removed by being slid vertically off of the ball stem and out of valve body bore, the full extent of the recess in the valve body located above the cylindrical sealing elements will be opened and, due to the spherical shape existing between the cylindrical members and the inner end of the end members, the cylindrical members are free to rotate along that spherical surface into the recess in the valve body which allows the one-piece ball and stem element to be removed vertically from the valve body without disengaging the ball valve assembly from its in-line position. Likewise, it is also possible to remove one or both of the separate cylindrical members.
In both embodiments the body seals adjacent the end members and the annular enclosing and sealing members are sealed by full circle compression seals which further help eliminate problems associated with body seals under high and low temperature conditions.